1. Field of the Invention
This invention relates to a process and an apparatus for supplying a primer and spraying air to a spray gun to spray the primer.
2. Description of Related Art
Previously, in the manufacture of a polymer insulator, for example, a primer (priming agent such as an adhesive) is applied onto an outer surface of a rod-shaped FRP core as a workpiece, and then a shed made of silicone rubber or the like is molded thereon. When applying the primer on the outer surface of FRP core, it is known to apply the primer through use of an airless spray gun or to apply the primer through a spray gun under an operation of a worker.
However, when of applying the primer by using conventional airless spray gun, several problems arise.
For instance, in order to apply the primer thinly and uniformly, it becomes necessary to decrease the amount of the primer sprayed. However, airless spray guns supplying such a small spraying amount are not commercially available.
Moreover, inknown airless spray guns, the spraying amount can be decreased by decreasing a spraying pressure. However the spraying state is not stable and hence the primer can not be applied thinly and uniformly.
Additionally, the primer tends to deposit around nozzle portion of the spray gun thereby stopping the spraying.
In order to avoid the deposition of the primer around the nozzle portion of the spray gun, it is necessary to use a large-scale installation for isolating the whole of the spraying apparatus from the atmosphere.
On the other hand, there are also problems associated with applying primer by using a conventional spray gun.
Even though the spraying amount smaller than that of the airless spray gun, the spraying amount is still relatively large in commercially available spray guns.
Even though the spraying amount can be decreased by lowering the spraying pressure and the pressure applied to a liquid surface of the primer, the spraying state will not be stable. Thus, In addition, spraying still stops because the primer still deposits around the nozzle portion of the spray gun the primer can not be applied thinly and uniformly.
In order to avoid the deposition of the primer around the nozzle portion of the spray gun, it is therefore still necessary to use a large-scale installation for isolating the whole of the spraying apparatus from an atmosphere.